There is an increasing demand for data packet services over a wireless communication system, and data packet services have been widely used. In order for data packet services to be used more efficiently, micromini mobile communication BSs have been installed in indoor environments such as home and office. The micromini mobile communication BSs installed in indoor environments are generally called a home BS (or in-building BS) or a femto BS, and users may freely enjoy wire/wireless communication services on Mobile Stations (MSs) or Mobile Subscriber Stations (MSSs) within a femto cell, which is a coverage or a service zone of the femto BS. On the other hand, a BS and a cell having the normal function and coverage are called a macro BS and a macro cell, respectively.
Mobile Worldwide Interoperability for Microwave Access (WiMAX) supports femto BSs having transmit power of 100 mW (20 dBm) or below to provide high-quality high-speed wireless Internet access services in the home and office environments, which is similar to providing the services over a macro BS having high transmit power of 20 W (43 dBm) or below. Unlike the macro BS having a cell radius of several kilometers, the femto BS has a cell radius of several meters to several tens of meters as its coverage and is installed in the home or office, maximizing the frequency reuse in the radio environment and thus providing the high-quality high-speed wireless Internet access services at significantly low prices compared with the macro network. The femto BS may communicate with MSs using the same air interface standard as that of the macro BS, such as, for example, IEEE 802.16e or IEEE 802.16m.
In order to guarantee service continuity for an MS while traveling between BSs, each BS is required to provide the MS with radio configuration information for its neighbor BSs. Unlike the existing macro network in which each BS has a maximum of ten neighbor BSs, the femto scenario provides a network environment in which one macro BS has hundreds or thousands of femto BSs as neighbor BSs or handover candidate BSs, which exist in its broad coverage having a radius of several square kilometers.
In this case, to manage and update information about neighbor BSs, each macro BS generally exchanges messages with a maximum of several thousands of neighbor femto BSs, which can be hardly achieved with performance of the hardware used in the communication equipment. Likewise, an Access Service Network-Gateway (ASN-GW) in the macro network, which interworks with hundreds of macro BSs, should also handle a very large number of messages in proportion to the number of managed macro BSs.